Messages in this thread | | | Subject | Re: [RFC] exponential update_wall_time | From | john stultz <> | Date | Wed, 27 Sep 2006 16:13:12 -0700 |
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On Thu, 2006-09-28 at 01:04 +0200, Roman Zippel wrote: > On Wed, 27 Sep 2006, john stultz wrote: > > > Accumulate time in update_wall_time exponentially. > > This avoids long running loops seen with the dynticks patch > > as well as the problematic hang" seen on systems with broken > > clocksources. > > This is the wrong approach, second_overflow() should be called every HZ > increment steps and your patch breaks this.
First, forgive me, since I've got a bit of a head cold, so I'm even slower then usual. I just don't see how this patch changes the behavior. Every second we will call second_overflow. But in the case where we skipped 100 ticks, we don't loop 100 times. Could you explain this a bit more?
> There are other approaches oo accommodate dyntick. > 1. You could make HZ in ntp_update_frequency() dynamic and thus reduce the > frequency with which update_wall_time() needs to be called (Note that > other clock variables like cycle_interval have to be adjusted as well).
I'm not sure how this is functionally different from what this patch does.
> 2. If dynticks stops the timer interrupt for a long time, it could > precalculate a few things, e.g. it could complete the second and then > advance the time in full seconds.
Not following this one at all.
Again, sorry for being so thick. -john
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